. >> so at the same time is your claim is, stronium and robidium, you can tell one with a mass spectrometer, those clocks were set 10,000 years ago, and when i observe light 10,000 years ago those were put there, that's your claim 87? >> well data is based on assumptions of the past. you don't know because you weren't there. >> no i wasn't there but i'm pretty sure we had a civil war. i'm pretty sure we had isaac newton, i'm pretty sure we had gal lai galileo. >> we're not going to get this solved today or any time soon but we want to thank all of our guests, bill, don, ca have i and georgia. thank you. bill, sit tight, we want to leave time for questions from our viewers outside of the topic today. waj, at a it away. >> what are the best ways to make science relatable and interesting to kids and adults? >> i say just mess around. i say this all the time. explore. when you explore, whether it's your baking soda and vinegar and a balloon or your backyard under threat of climate change fire right now, that's an assertion, under threat of fire is yosemite national park, you'll have two things